Manipulate[
 Module[{pa = p1, pt = p2, d, od},
  d = EuclideanDistance[pa, pt];
  od = VectorAngle[{1, 0}, pt - pa]*180/Pi;
  Graphics[{
    Line[{pa, pt}],
    Text["两点距离:" <> ToString[d~SetPrecision~2], {9, 4}, {-1, 1}],
    Text["两点水平夹角:" <> ToString[od~SetPrecision~3], {9, 3}, {-1, 1}]
    }, PlotRange -> {{-2, 13}, {-1, 5}},
   Axes -> True, GridLines -> {None, {pa[[2]]}}]
  ],
 {{p1, {0., 1}}, Locator}, {{p2, {2, 2}}, Locator}
 ]
